I was one of the first to buy a guidegun, picked it up in Kittery Maine, this was a ported 1895M guidegun, I'm a reloader and I can tell you the case is much stronger, thicker webwalls, In tern the 45/70 case can hold more water weight a few grs more powder, the 450 case has much better construction compared to a 45/70 case, The 450 Marlin seems to be a better shooter than any 45/70 I ever shot, I'm grouping clover leaf at 100 yards using a Hornady 350gr FN Interlock using 50gr H4198, CCI mag primers 2180 fps, seems the 450 Marlin creates more power with less powder as well, Its all chambering, dame thing is loud when you let off, if you don't have ear protection on your ears will ring for hours not good, does keep the muzzle down. I love my 1895M guidegun, I have harvested a Black bear and a German boar so far using my reloads. Had no problem expiring my game. I would never turn back, I just never liked the 45/70 case, always had a weak look to it, you can pinch one between your fingers, try doing that with 450 brass;) I know there is those die hards that just love there 45/70, thats fine as well. To each there own
Aim small hit small. RAMbo.